Using the Subtract transformation in CoffeeScad to create a thru-hole or a hollow object.

HoleExample.coffee

# How to create a hole

# First, create the object we want to put a hole in
disc = new Cylinder
  d: 100
  h: 10
  center: true
  
# Next, create a cylinder the size of the hole
hole = new Cylinder
  d: 25
  h: 11
  center: true
  
# Finally, using the subtract transformation, subtract
# the cylinder from the disc, leaving a disc with a
# hole in the middle

holeyDisc = disc.subtract(hole)

return holeyDisc

HollowBox.coffee

# How to create a hollow box

# First, create a rectangle the size of the box.
box = new Cube
  size: [60,40,20]
  center: [0,0,10] # Move the box up so it sits on the XY plane
  
# Next, create a rectangle the size of the inside.
hole = new Cube
  size: [55,35,18]
  center: [0,0,11.5] # This size and position will leave a 2.5 unit thick wall and bottom.
  
# Finally, using the subtract transformation, subtract
# the inside from the outside

box = box.subtract(hole)

return box